51238-M bearing: complete specifications & equivalents

Specification table

Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-28

Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018)); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.

Cross references & equivalents

Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.

How the 51238-M model number is decoded

51238 M is SKF's 190 mm-bore single-direction thrust ball bearing in the 51200 series to the ISO 104 dimension plan, with a flat housing seating surface, measuring 190×270×62 mm. The separable set comprises a shaft washer (ground bore, tight fit on the shaft), a loose-bore housing washer and one ball-cage assembly, reacting axial force in one direction and carrying no radial load. in the 51xxx designation the first 1 marks a single-direction bearing with a flat housing seating surface; the third digit 1–4 grades the dimension series from the light 511 section through the heavy 514 section. the final two digits 38 encode the bore as 190 mm (code 38 × 5), the standard SKF bore-code rule shared with radial bearings. suffix M identifies a one-piece machined brass cage, ball-centred: the large-size and heavy-section option for higher speeds, shock loads and thin-film lubrication where a pressed cage would distort. Envelope 190×270×62 mm (7.48×10.63×2.441 in), 40.0 mm radial section, C 332 kN, C0 1270 kN, Pu 31 kN. reference speed 1,100 r/min (thermal) and limiting speed 1,600 r/min (mechanical), catalogue mass 12000 g. Stack/annulus proportions: the 62 mm axial stack over the 28,903 mm² washer annulus gives 2.15 mm of height per annular square millimetre ×10⁻³, and at 12000 g the bearing holds about 105.8 kN of C0 per kilogram. Track-circle loading: per millimetre of mean track circumference the 332 kN dynamic rating corresponds to roughly 0.46 kN/mm of π·dm track, a useful comparison against the other dimension series of the 190 mm bore. Preload at the mechanical ceiling: repeating Fam ≈ A·(n·dm/1000)² with factor A 8.4 at the 1,600 r/min limiting speed raises the required axial preload to about 1137.6 kN; the reference-speed value 537.7 kN is the thermal design point. Light-load floor: Pu = 31 kN is the equivalent-load threshold below which the SKF adjusted-life equation credits very long life for 51238 M; the number is 9 % of the 332 kN dynamic rating. At the printed limiting speed of 1,600 r/min the mean pitch diameter dm ≈ 230.0 mm implies a dn value around 368k mm·r/min; the 1,100 r/min reference speed is the thermal-planning value under catalogue load. Machined-cage order-number note: the M brass cage is a one-piece ball-centred window cage, chosen at the heavy end of the section for speed and shock duty; it is heavier and stiffer than the pressed-steel execution of the smaller sizes and tolerates interrupted lubrication far better, which is why the catalogue restricts the M suffix to the large bores. At 12000 g the machined brass cage represents a meaningful fraction of total mass; balancing checks on high-speed 190 mm vertical shafts should use the actual M-execution weight, not the lighter pressed-cage catalogue value.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• The third digit grades the section: 511 light, then 512, 513 and 514 progressively taller and heavier at the same bore — select from 332/1270 kN and the available 270 mm OD, never substitute a lighter series for a heavier one without rechecking C and C0.
• A 51-series bearing reacts thrust in one direction only — reversing positions need a mirrored single-direction pair or a 52-series double-direction unit; fitting a single 51238 against two-way load lifts the loose washer off its raceway.
• The three components are separable and interchangeable within the ISO 104 size, but keep this bearing's parts together in service and never combine washers from different manufacturers or a worn washer with a new ball set.
• Heat the shaft washer to at most 120 °C for mounting, or press it via a sleeve on its ground bore — force applied through the housing washer or the ball set brinells the 332 kN track before first rotation.
• Ordering discipline for 51238: the catalogue page quotes 51238 M and its 332/1270 kN ratings as one exact article; bare-number substitutions from another series or brand need a fresh dimension and rating check, not a like-for-like assumption.